1. Field of the Invention
The present invention relates to an apparatus for driving light emitting diode (LED) arrays, and more particularly, to an apparatus for driving a plurality of red, green and blue LED arrays used as a direct-type LCD backlight, in which fewer number of parts are required to minimize the apparatus and save manufacturing costs thereof.
2. Description of the Related Art
A cold cathode fluorescent lamp (CCFL) has been conventionally utilized as a light source of a light crystal display (LCD) backlight. The CCFL may trigger environmental pollution due to use of a mercury gas. Also, the CCFL is low in response rate and color reproducibility, and inadequate for reducing the weight and size of an LCD panel.
In contrast, a light emitting diode (LED) is environment-friendly and can respond fast with several nano seconds, thus effective in video signal stream. Moreover, the LED can be impulsively driven, reproduce colors by 100% or more and arbitrarily change brightness and color temperature by adjusting a light amount of red, green and blue LEDs. Also, the LED carries advantages leading to a lighter weight and smaller sized LCD panel. Thus the LED is actively adopted as a backlight source of the LCD panel.
In general, the LCD backlight employing the LEDs includes an edge-type backlight and a direct-type backlight depending on location of a light source. In the former, a light source is shaped as an elongated bar and disposed at a side of a light guide plate to irradiate light onto the LCD panel. In the latter, a surface light source is substantially identical in size to the LCD panel and disposed under the LCD panel to directly irradiate light onto the LCD panel.
Meanwhile, a white light emitting diode has yet to be developed. Thus, typically, the LED for use in the LCD backlight generates white light by combining a red LED, a green LED and a blue LED together. To emit white light uniformly onto an entire area of the LCD, various LED arrangements have been studied. Also, under development are technologies for properly controlling brightness and colors of the LCD backlight by effectively supplying a driving current (driving voltage) to the LEDs of each color.
FIG. 1 is a block diagram illustrating an example of a conventional apparatus for driving LED arrays. Referring to FIG. 1, the conventional apparatus for driving LED arrays include a plurality of LED array driving boards 10. Typically, a light source 20 used as an LCD backlight is provided with a plurality of red, green and blue LED arrays 21, 22, and 23 on a board. To effectively drive the LED arrays, one or more LED arrays 21, 22 and 23 are fabricated as a module or arranged in a predetermined area. Here, each of the LED array driving boards 10 is provided to the LED arrays of each color 21, 22 and 23 located in the module or area.
The LED array driving boards 10 each include a dimming/size setter 11, red/green/blue PWM controllers 121, 131 and 141, and DC/DC converters 122, 132 and 142. The dimming/size setter 11 sets a driving voltage to be supplied to the LED arrays 21, 22, and 23 of each color in response to a dimming control signal SD and a size control signal SA inputted from inside and outside. The red/green/blue PWM controllers 121, 131 and 141 each generate a PWM control signal to supply the driving voltage set by the dimming/size setter 11 to the LED arrays of each color 21, 22 and 23. The DC/DC converters 122, 132 and 142 generate static power by phase width modulation (PWM) in response to the PWM control signal.
In the conventional apparatus for driving LED arrays configured as above, an LED array driving board is required to drive the red/green/blue LEDs located in a module or a predetermined area. Thus, increase in the number of modules or blocks having the LED arrays therein leads to increase in the number of the driving boards and accordingly the number of parts required for the driving apparatus. This consequently adds to the size and volume of the driving apparatus, which thus should be installed in a larger area. This adversely affects miniaturization of the product and increments costs for manufacturing or purchasing the parts, thereby raising manufacturing costs.